1. Field of the Invention
This invention relates generally to data processing systems and, more particularly, to object oriented programming systems and processes.
2. Description of the Related Art
Computer programs have typically been developed using procedural programming techniques. Procedural programming techniques emphasize structuring the data processing procedures to which data values are subjected. Efforts to reduce long software development times and high software maintenance costs have resulted in structured programming techniques that attempt to reuse blocks of programming code. For example, tasks or processes that must be repeated can be written as system programming routines or program library functions. Program developers then provide an application program to accomplish a desired result using calls to the system routines and library functions.
System routines and library functions provide only a limited reduction in software development time and maintenance costs. Once a procedural application program is written, it is relatively difficult to incorporate new features or additional data types. There are many processes in an application program that cannot be easily extracted from program code and reused. Additional data types often cannot be inserted into procedural program code without extensive rewriting of the original program code. Thus, even if new features in a program can be implemented using processes similar to those already in the application, the programming for such processes must be largely duplicated, with slight modifications, to provide the new features. This increases program development time. Moreover, if such programs must operate with other applications, it can be difficult to ensure that the changes will interface properly.
Another problem confronting program developers is that of providing program versions capable of operating with the various platforms used by customers. The different platforms encompass different operating systems as well as different companion applications with which the application must interface. With respect to operating systems, for example, a program developer might have to write different versions for satisfactory operation under the "Windows 95" operating system by Microsoft Corp., the UNIX system, the "MacIntosh" operating system by Apple Computer Corp., or the "OS/2" operating system by International Business Machines Corporation (IBM Corporation). In a similar fashion, a program developer might want to provide the ability to interface with application programs such as word processor programs, spreadsheet programs, and the like, meaning that the program developer must provide the ability to accept files (and produce files) in different file formats. Different platforms use different data formats and procedural operations, so program developers must provide different program versions or routines for each platform.
Object oriented programming (OOP) techniques encapsulate, or bind together, data and the methods that operate on them. This permits program development to more closely model real-world systems for problem solution and breaks up program development efforts into smaller, more manageable pieces. OOP programs are developed around object classes that have attributes, also called data values, and methods, also called functions. Although OOP techniques have done much to improve program development efficiency, such techniques still require a great degree of code generation on the part of application developers and limit program reuse among different classes.
OOP frameworks have been developed in an effort to further reduce program development costs. A framework is a set of OOP classes that embodies a predetermined set of attributes and methods for providing a common group of behaviors. An application program developer utilizes the framework and builds upon it, adding subclasses and attributes and modifying methods depending on the problem to be solved. Such changes to the framework are typically referred to as framework extensions, and are made possible by the OOP notions of inheritance and polymorphism. The challenge confronting framework developers, then, is to arrive at a set of classes and methods that will best provide the desired problem solution and will accept the most likely framework extensions. Thus, the designer of a framework must carefully assess what framework users will most likely need in the way of classes and attributes.
From the discussion above, it should be apparent that there is a need for an application program development tool that permits application program developers to more quickly develop and more easily maintain business financial applications such as accounts receivable and accounts payable software. The present invention fulfills this need.